Continuous Gradations Research Articles

Thermal Stress Analysis for Functionally Graded Plates with Modulus Gradation, Part II

BackgroundThe gradation of thermal expansion coefficient was analyzed in the earlier study. The analytical formulation derived here, which is quite different, should be validated to understand the thermal stress distribution in a laminated composite and functionally graded material. Besides this solution, a validated numerical model can also be used to optimize the material gradation of plates in terms of sustainability.ObjectiveTo validate the analytical formulation derived here, an experimental model is presented to understand the thermal stress concentration for functionally graded and laminated composite plates. A numerical model is also validated to extend to understand the effects of the number of layers, the thickness of a layer, the gradation function, the ratio of elastic moduli, and the coating.MethodsThe experimental problems in the production of the experimental models with layers of different elastic moduli are discussed here. In the experimental analysis, a three-dimensional photoelastic stress analysis of two- and four-layer composite plate was used to mechanically model the thermal expansion. The analytical solution for the thermal stress in a free plate was derived by the strain suppression method based on the principle of superposition. The numerical models were analyzed using finite element software. The step variation in the experiment was used as a reference point for a continuous or multi-layer (> 2) step variation of material coefficients in the models.ResultsThe variation of stress concentration is shown for various cases of laminated and continuous gradations of elastic modulus. The four-layer experimental model provides the difference in thermal stress distribution as a result of a layered coating. The validated analytical and numerical models provide reasonable results. An empirical formula to optimize the material gradation in terms of elastic modulus is derived.ConclusionsThe experimental model can be used to analyze thermal stress in functionally graded materials. The gradations of the material in the plate or the coating of the plates can be optimized by the validated analytical and numerical models. The empirical formula can be used to determine the elastic modulus of the coating to minimize the stress concentration.

Continuous sensing of nutrients and growth factors by the mTORC1-TFEB axis.

mTORC1 senses nutrients and growth factors and phosphorylates downstream targets, including the transcription factor TFEB, to coordinate metabolic supply and demand. These functions position mTORC1 as a central controller of cellular homeostasis, but the behavior of this system in individual cells has not been well characterized. Here, we provide measurements necessary to refine quantitative models for mTORC1 as a metabolic controller. We developed a series of fluorescent protein-TFEB fusions and a multiplexed immunofluorescence approach to investigate how combinations of stimuli jointly regulate mTORC1 signaling at the single-cell level. Live imaging of individual MCF10A cells confirmed that mTORC1-TFEB signaling responds continuously to individual, sequential, or simultaneous treatment with amino acids and the growth factor insulin. Under physiologically relevant concentrations of amino acids, we observe correlated fluctuations in TFEB, AMPK, and AKT signaling that indicate continuous activity adjustments to nutrient availability. Using partial least squares regression modeling, we show that these continuous gradations are connected to protein synthesis rate via a distributed network of mTORC1 effectors, providing quantitative support for the qualitative model of mTORC1 as a homeostatic controller and clarifying its functional behavior within individual cells.

Red and blue states: dichotomized maps mislead and reduce perceived voting influence

In the United States the color red has come to represent the Republican party, and blue the Democratic party, in maps of voting patterns. Here we test the hypothesis that voting maps dichotomized into red and blue states leads people to overestimate political polarization compared to maps in which states are represented with continuous gradations of color. We also tested whether any polarizing effect is due to partisan semantic associations with red and blue, or if alternative hues produce similar effects. In Study 1, participants estimated the hypothetical voting patterns of eight swing states on maps with dichotomous or continuous red/blue or orange/green color schemes. A continuous gradient mitigated the polarizing effects of red/blue maps on voting predictions. We also found that a novel hue pair, green/orange, decreased perceived polarization. Whether this effect was due to the novelty of the hues or the fact that the hues were not explicitly labeled “Democrat” and “Republican” was unclear. In Study 2, we explicitly assigned green/orange hues to the two parties. Participants viewed electoral maps depicting results from the 2020 presidential election and estimated the voting margins for a subset of states. We replicated the finding that continuous red/blue gradient reduced perceived polarization, but the novel hues did not reduce perceived polarization. Participants also expected their hypothetical vote to matter more when viewing maps with continuous color gradations. We conclude that the dichotomization of electoral maps (not the particular hues) increases perceived voting polarization and reduces a voter’s expected influence on election outcomes.

Spectral Characteristics of the Dynamic World Land Cover Classification

The Dynamic World product is a discrete land cover classification of Sentinel 2 reflectance imagery that is global in extent, retrospective to 2015, and updated continuously in near real time. The classifier is trained on a stratified random sample of 20,000 hand-labeled 5 × 5 km Sentinel 2 tiles spanning 14 biomes globally. Since the training data are based on visual interpretation of image composites by both expert and non-expert annotators, without explicit spectral properties specified in the class definitions, the spectral characteristics of the classes are not obvious. The objective of this study is to quantify the physical distinctions among the land cover classes by characterizing the spectral properties of the range of reflectance present within each of the Dynamic World classes over a variety of landscapes. This is achieved by comparing both the eight-class probability feature space (excluding snow) and the maximum probability class assignment (label) distributions to continuous land cover fraction estimates derived from a globally standardized spectral mixture model. Standardized substrate, vegetation, and dark (SVD) endmembers are used to unmix nine Sentinel 2 reflectance tiles from nine spectral diversity hotspots for comparison between the SVD land cover fraction continua and the Dynamic World class probability continua and class assignments. The variance partition for the class probability feature spaces indicates that eight of these nine hotspots are effectively five-dimensional to 95% of variance. Class probability feature spaces of the hotspots all show a tetrahedral form with probability continua spanning multiple classes. Comparison of SVD land cover fraction distributions with maximum probability class assignments (labels) and probability feature space distributions reveal a clear distinction between (1) physically and spectrally heterogeneous biomes characterized by continuous gradations in vegetation density, substrate albedo, and structural shadow fractions, and (2) more homogeneous biomes characterized by closed canopy vegetation (forest) or negligible vegetation cover (e.g., desert, water). Due to the ubiquity of spectrally heterogeneous biomes worldwide, the class probability feature space adds considerable value to the Dynamic World maximum probability class labels by offering users the opportunity to depict inherently gradational heterogeneous landscapes otherwise not generally offered with other discrete thematic classifications.

Joint Characterization of Sentinel-2 Reflectance: Insights from Manifold Learning

Most applications of multispectral imaging are explicitly or implicitly dependent on the dimensionality and topology of the spectral mixing space. Mixing space characterization refers to the identification of salient properties of the set of pixel reflectance spectra comprising an image (or compilation of images). The underlying premise is that this set of spectra may be described as a low dimensional manifold embedded in a high dimensional vector space. Traditional mixing space characterization uses the linear dimensionality reduction offered by Principal Component Analysis to find projections of pixel spectra onto orthogonal linear subspaces, prioritized by variance. Here, we consider the potential for recent advances in nonlinear dimensionality reduction (specifically, manifold learning) to contribute additional useful information for multispectral mixing space characterization. We integrate linear and nonlinear methods through a novel approach called Joint Characterization (JC). JC is comprised of two components. First, spectral mixture analysis (SMA) linearly projects the high-dimensional reflectance vectors onto a 2D subspace comprising the primary mixing continuum of substrates, vegetation, and dark features (e.g., shadow and water). Second, manifold learning nonlinearly maps the high-dimensional reflectance vectors into a low-D embedding space while preserving manifold topology. The SMA output is physically interpretable in terms of material abundances. The manifold learning output is not generally physically interpretable, but more faithfully preserves high dimensional connectivity and clustering within the mixing space. Used together, the strengths of SMA may compensate for the limitations of manifold learning, and vice versa. Here, we illustrate JC through application to thematic compilations of 90 Sentinel-2 reflectance images selected from a diverse set of biomes and land cover categories. Specifically, we use globally standardized Substrate, Vegetation, and Dark (S, V, D) endmembers (EMs) for SMA, and Uniform Manifold Approximation and Projection (UMAP) for manifold learning. The value of each (SVD and UMAP) model is illustrated, both separately and jointly. JC is shown to successfully characterize both continuous gradations (spectral mixing trends) and discrete clusters (land cover class distinctions) within the spectral mixing space of each land cover category. These features are not clearly identifiable from SVD fractions alone, and not physically interpretable from UMAP alone. Implications are discussed for the design of models which can reliably extract and explainably use high-dimensional spectral information in spatially mixed pixels—a principal challenge in optical remote sensing.

Internal Erosion Experiments on Sandy Gravel Alluvium in an Embankment Dam Foundation Emphasizing Horizontal Seepage and High Surcharge Pressure

For an internally unstable soil, fine particles can move in the pore channels between coarse particles along with seepage flow; this process is termed internal erosion. To evaluate the internal stability and internal erosion behavior of sandy gravel alluvium beneath the suspended cutoff wall in an embankment dam foundation, a series of horizontal seepage tests were carried out on the four representative gradations of the alluvium layer using a large-scale high-pressure erosion apparatus. The evolutionary trends of hydraulic conductivity, the erosion ratio of fine particles, and volumetric strain under stepwise increasing hydraulic loading were obtained. The results showed that the specimens of different gradations exhibited distinct properties in permeability, particle loss, and deformation, depending on the gradation continuity and fine particle content, which can be attributed to the difference in the composition of the soil skeleton and the arrangement of coarse and fine particles. For the specimens with continuous gradations or relatively high fine particle content, the surcharge pressure can significantly improve their internal stability. By contrast, in the situations of gap-graded gradations or low fine particle content, no considerable improvement was found because the stress was mainly borne by the coarse skeleton. The practical implications of the experimental results were demonstrated by evaluating the seepage safety of the zone beneath the suspended wall in the dam foundation.

Determining concrete properties for different optimized combined concrete mixtures: Novel mathematical approach

Gradation of the granular skeleton significantly influences almost all of the concrete performances. The main purpose of this research work is to develop a mathematical model to characterize the properties of various dry concrete mixtures. The starting point of this work is to propose a single equation to describe continuous aggregate gradations, by combining several ideal grading curves used to design different concrete mixtures, to achieve higher freedom in optimizing the particle-size distribution (PSD) of a concrete mixture. At the design procedure stage, the concrete constituents are selected so that the overall grading of the mix closely follows a given ideal grading curve for specific properties. Using the gradation equation afore-mentioned, a mathematical framework is established to outline several intrinsic factors in the optimized granular skeleton of concrete, characterized by a wide range of particle sizes. The factors developed, directly measured based on the PSD, include the specific surface area and the fineness modulus of the combined grading of the concrete mix particles, as well as the ratio between the granular fractions determined either by area or by weight, and the surface area of the total concrete mixture. The resulting model expressions relate the characteristics of the size distribution of the concrete skeleton, to the parameters in the proposed gradation equation, in particular the distribution exponent. The proposed model could be implemented in the study of the solid phase of concrete, design aggregate gradation to meet certain requirements, or even predict some attributes of the dry concrete mixture. • A unified equation of well-known optimal particle size distributions is developed. • A model is proposed to accurately calculate some properties of the concrete mixes. • The distribution exponent in the proposed equation is the most relevant parameter. • Optimal PSDs are fractal and converge mathematically to the Fung & Dinger model. • The proposed model is suitable for systems with a wide range of particle sizes.

Optimization of energy absorption performance of polymer honeycombs by density gradation

Density gradation has been analytically and experimentally proven to enhance the load-bearing and energy absorption efficiency of cellular solids. This paper focuses on the analytical optimization (by virtual experiments) of polymeric honeycomb structures made from thermoplastic polyurethane to achieve density-graded structures with combined desired mechanical properties. The global stress-strain curves of single-density honeycomb structures are used as input to an analytical model that enables the characterization of the constitutive response of density-graded hexagonal honeycombs with discrete and continuous gradations and for various gradients. The stress-strain outputs are used to calculate the specific energy absorption, efficiency, and ideality metrics for all density-graded structures. The analytical results are shown to be in good agreement with previous experimental measurements. Our findings suggest that the choice of an optimal gradient depends on the specific application and design criteria. For example, graded structures wherein low density layers are dominant are shown to outperform high density uniform honeycombs in terms of specific energy absorption capacity while possessing higher strength compared with low density uniform structures.

Three-dimensionally-printed anthropomorphic physical phantom for mammography and digital breast tomosynthesis with custom materials, lesions, and uniform quality control region.

Anthropomorphic breast phantoms mimic patient anatomy in order to evaluate clinical mammography and digital breast tomosynthesis system performance. Our goal is to create a modular phantom with an anthropomorphic region to allow for improved lesion and calcification detection as well as a uniform region to evaluate standard quality control (QC) metrics. Previous versions of this phantom used commercial photopolymer inkjet three-dimensional printers to recreate breast anatomy using four surfaces that were fabricated with commercial materials spanning only a limited breast density range of 36% to 64%. We use modified printers to create voxelized, dithered breast phantoms with continuous gradations between glandular and adipose tissues. Moreover, the new phantom replicates the low-end density (representing adipose tissue) using third party material, Jf Flexible, and increases the high-end density to the density of glandular tissue and beyond by either doping Jf Flexible with salts and nanoparticles or using a new commercial resin, VeroPureWhite. An insert design is utilized to add masses, calcifications, and iodinated objects into the phantom for increased utility. The uniform chest wall region provides a space for traditional QC objects such as line pair patterns for measuring resolution and scale bars for measuring printer linearity. Incorporating these distinct design modules enables us to create an improved, complete breast phantom to better evaluate clinical mammography systems for lesion and calcification detection and standard QC performance evaluation.

Mechanical properties of porous concrete with variations of coarse aggregate gradation

Porous concrete is an innovation in sustainable concrete technology, which has high porosity concrete without fine aggregate. Porous concrete used in rain gardens, planter boxes, permeable pavements at urban open spaces could absorb rainwater so it can reduce run-off. This experimental study purposes to determine the compressive, split-tensile, flexural strengths, and permeability of porous concrete with various gradation of coarse aggregates. This study used a concrete mixture with coarse aggregate gradation variations of gap, continuous, and uniform on the water cement ratio of 0.4. The test specimens used three cylinders of 15x30cm for compressive and split-tensile strengths, except for uniform gradations used three cylinders of 10x20cm. Beam specimens of 15x15x60cm used for bending strength test by third point loading method. The tested mechanical properties are 7, 14, and 28 days-compressive strengths, 28 days split-tensile strength, and 28 days bending strength. The experimental results also show the average compressive strengths of porous concrete with variation of gradations of gap, continuous, and uniform for 28 days is 14.6 MPa, 13.0 MPa, and 10.6 MPa, respectively. Volumetric flow rate of porous concrete with gap, continuous, and uniform aggregate gradations is 28.4 ml/s, 32.1 ml/s, and 39.3 ml/s, respectively. The experimental results show that gap gradation is recommended due to its better compressive and flexural strengths. In porous concrete, aggregate gradations influence the air content. The highest air content results the lowest compressive strength of concrete. The designed air content should be controlled to maintain the expexted compressive strength of porous concrete.

BAHAN TAMBAH SERAT ECENG GONDOK PADA LASTON TIPE XI TERHADAP INDEKS MARSHALL TEST MENGGUNAKAN KERIKIL MANTUP

Laston is a mixture of coarse aggregate, fine aggregate, and filler with a binder under the temperature of 145-155oC with the composition being studied and regulated by technical specifications. Laston is also known as AC (Asphalt Concrete).Laston itself is commonly used in Indonesia with continuous gradations used for heavy traffic loads. To get the addictive material is not easy and the material is expensive. Therefore, it is necessary to find alternatives to the cellulose fiber. Water hyacinth is a water weed that once grow and develop, it has high cellulose fiber content, which is about 60%.For that, done a research to add a hot asphalt mixture material that aims to improve the quality of mixed result. The selected material is natural water hyacinth. The method used is trial and error with reference of SNI 03-1737-1989. Variations used are 3%, 5%, and 7% of the asphalt weight, asphalt level used Is 5.61%.The result of this study is Marshall evaluation where the greatest score obtained for stability is 1325 kg, Flow is 3.73 mm, Quotient Marshall is 401.02 kg/mm, VMA is 66.30%, VFWA is 19.25%, and VIM score is 54.35 %. With this result, the asphalt mixture can not be used because the results of VMA, VFWA, and VIM have not been suitable on specification of SNI 03-1737-1989. Keywords: Laston, Asphalt Concrete, Water Hyacinth, SNI 03-1737-1989.

Are Alcohol Trajectories a Useful Way of Identifying At-Risk Youth? A Multiwave Longitudinal-Epidemiologic Study

Trajectory approaches are a popular way of identifying subgroups of children and adolescents at high risk for developing alcohol use problems. However, mounting evidence challenges the meaning and utility of these putatively discrete alcohol trajectories, which can be analytically derived even in the absence of real subgroups. This study tests the hypothesis that alcohol trajectories may not reflect discrete groups-that the development of alcohol use is continuous rather than categorical. A multiwave longitudinal-epidemiologic twin study was conducted using 3,762 twins (1,808 male and 1,954 female) aged 11 to 29 years from the Minnesota Center for Twin and Family Research (MCTFR). The main outcome measures included various assessments of substance use, psychopathology, personality, and cognitive ability. Although multiple trajectories are derived from growth mixture modeling techniques, these trajectories are arrayed in a tiered spectrum of severity, from lower levels of use to higher levels of use. Trajectories show perfect rank-order stability throughout development, monotonic increases in heritability, and perfect rank-order correlations with established correlates of alcohol use, including other substance use behaviors, psychiatric disorders, personality traits, intelligence, and achievement. Alcohol trajectories may represent continuous gradations rather than qualitatively distinct subgroups. If so, early detection and interventions for youth based on trajectory subtyping will be less useful than continuous liability assessments. Furthermore, a continuous account of development counters the notion that individuals are predestined to follow one of a few categorically distinct pathways and promotes the opposite idea-that development is mutable, and its continuous terrain can be traversed in many directions.

Forest classes and tree cover gradient: tick habitat in encroached areas of southern Norway.

Forest, in particular deciduous forest, is a key element in determining areas with a high probability of tick presence. The way forest is generally monitored may be ill suited to some landscapes where Ixodes ricinus is found, as forest is usually characterised using crisp land cover classes. However, tree vegetation can be found outside of forests and continuous gradations of tree density can be found in a variety of landscapes. In this paper we investigate the probability of tick presence in southern Norway using landscape description based both on land cover classes and continuous data describing the tree cover fraction. Both perspectives on the landscape are significant in the logistic model, indicating that the usual approach based solely on land cover classes may not be comprehensive enough in capturing tick habitat, and characterising the landscape with variables focused on single specific elements may be insufficient.

Electrospun fibrous scaffolds with continuous gradations in mineral contents and biological cues for manipulating cellular behaviors

Challenges remain in the generation of heterogeneous tissues and the repairing of interfacial tissue between soft and hard tissues. The development of tissue engineering scaffolds with gradients in composition, structure, mechanical and chemical properties is essential to modulate cellular behaviors in a graded way and potentially support the growth of functionally graded tissues. Integrated with the three-dimensional (3-D) nanofibrous skeletal structure of native extracellular matrix, electrospun fibers with gradients in amino groups were generated in the current study through an aminolysis process by using a microinfusion pump. Gelatin grafts were constructed to create fibrous scaffolds with gradients in hydroxyapatite (HA) contents, crystal size and mechanical properties through in situ mineralization. Plasmid DNA (pDNA) was included during the mineralization process, and gradations in pDNA loading contents were created on fibrous scaffolds on the basis of HA gradients. Obvious gradients in cell density, osteoblastic differentiation and collagen deposition were demonstrated along the long axis of fibrous mats after cell seeding. Gradients in the amount of pDNA released and the expression of target proteins were indicated on the fibrous mats, which offered a temporally and spatially controlled delivery of growth factors in scaffolds. The creation of gradient futures on 3-D fibrous scaffolds may provide physical, chemical and biological cues and result in efficient regeneration of tissues with spatial distributions of the cell proliferation, differentiation, and matrix secretion.

Effects of Material Gradation on Thermo-Mechanical Stresses in Functionally Graded Beams

The aim of this paper is to study the effects of material gradation on thermo-mechanical stresses in functionally graded beams. The composition of the beam varies gradually from ceramic to metal along both the thickness and width directions. Continuous gradations according to both the power law and exponential law variations are considered. In the presence of a thermal gradient and transverse distributed loads an analytical solution based on the Euler-Bernoulli beam theory is presented. Numerical sample where material gradations vary along both the thickness and width directions is carried out. It is found that the gradation of materials affects the neutral axis position.

Functionally graded β‐TCP/PCL nanocomposite scaffolds: In vitro evaluation with human fetal osteoblast cells for bone tissue engineering

The engineering of biomimetic tissue relies on the ability to develop biodegradable scaffolds with functionally graded physical and chemical properties. In this study, a twin-screw-extrusion/spiral winding (TSESW) process was developed to enable the radial grading of porous scaffolds (discrete and continuous gradations) that were composed of polycaprolactone (PCL), beta-tricalciumphosphate (beta-TCP) nanoparticles, and salt porogens. Scaffolds with interconnected porosity, exhibiting myriad radial porosity, pore-size distributions, and beta-TCP nanoparticle concentration could be obtained. The results of the characterization of their compressive properties and in vitro cell proliferation studies using human fetal osteoblast cells suggest the promising nature of such scaffolds. The significant degree of freedom offered by the TSESW process should be an additional enabler in the quest toward the mimicry of the complex elegance of the native tissues.

Functionally graded electrospun polycaprolactone and β-tricalcium phosphate nanocomposites for tissue engineering applications

Fabricating functionally graded scaffolds from biodegradable polymers to enable the mimicking of native tissue is an important challenge. Here we demonstrate the fabrication and utilization of functionally graded non-woven meshes of polycaprolactone incorporated with tricalcium phosphate nanoparticles using a new hybrid twin-screw extrusion/electrospinning (TSEE) process, which allows the time-dependent feeding of various solid and liquid ingredients and their melting, dispersion, deaeration and pressurization together with electrospinning within the confines of a single process. Using this hybrid method, the concentration of tricalcium phosphate nanoparticles could be tailored to vary in a targeted/controlled manner between the two surfaces of the scaffold mesh. The graded scaffolds were seeded and cultured with mouse preosteoblast cells (MC3T3-E1). Within 4 weeks, the tissue constructs revealed the formation of continuous gradations in extracellular matrix with various markers including collagen synthesis and mineralization, akin to the type of variations observed in the typical bone-cartilage interface in terms of the distributions of concentration of Ca particles and of mechanical properties associated with this. The demonstrated hybrid method should allow much better control of the distributions of various ingredients, including the concentrations of drugs/growth factors, as well as the porosity, mechanical property, wettability, biodegradation rate distributions in tissue engineering scaffolds, aiming to mimic the elegant complex distributions found in native tissue.

Developmental Dynamics and G-Matrices: Can Morphometric Spaces be Used to Model Phenotypic Evolution?

Modern morphometrics, especially geometric morphometrics, is a powerful tool for modeling the evolution and development of the phenotype. Complicated morphological transformations can be simulated by using standard evolutionary genetic equations for processes such as selection and drift in the same morphospaces that are used for empirical morphometric studies. Such applications appear to be consistent with the theory of quantitative evolution of the phenotype. Nevertheless, concerns exist whether simulations of phenotypic changes directly in morphospaces is realistic because trajectories traced in such spaces describe continuous gradations in the phenotype and because the gain and loss of structures is often impossible because morphospaces are necessarily constructed from variables shared in common by all the phenotypes being considered. Competing models of phenotypic change emphasize morphological discontinuity and novelty. Recently developed models of phenotypic evolution that introduce a “phenotypic landscape” between evolutionary genetic constructs like the adaptive landscape and morphospace may correct this shortcoming.

A comparison of the classification of wetland characteristics by linear spectral mixture modelling and traditional hard classifiers on multispectral remotely sensed imagery in southern India

An attempt has been made to compare the recently evolved soft classification method based on linear spectral mixture modelling (LSMM) with the traditional hard classification methods based on iterative self-organizing data analysis (ISODATA) and maximum likelihood classification (MLC) algorithms, in order to map and monitor the coastal wetland ecosystems of southern India, using Indian Remote Sensing Satellite (IRS) 1C/1D LISS-III and Landsat-5 Thematic Mapper (TM) image data. ISODATA and MLC methods were attempted to produce maps of 5, 10, 15 and 20 wetland classes for each of Pitchavaram, Vedaranniyam and Rameswaram sites. The accuracy of the derived classes was assessed with the simplest descriptive statistic technique called overall accuracy and the discrete multivariate technique called KAPPA accuracy. We found that MLC classification method produced maps with higher accuracy than ISODATA classification method. However, there was a systematic decrease in overall accuracy and KAPPA accuracy, when more number of classes were aimed to be derived from IRS-1C/1D and Landsat-5 TM imagery by ISODATA and MLC, caused by the limited spectral separability and instantaneous field of view (IFOV) of the sensor. The later one inevitably caused occurrence of number of mixture pixels (mixels) in the image and its effect on the classification process was a major problem to derive accurate wetland cover types, inspite of the increasing spatial resolution of new generation Earth Observation Sensors (EOS). To achieve higher accuracy of deriving wetland cover information from these data, a soft classification method based on linear spectral mixture modelling was presented. This method considered number of reflectance end-members that form the scene spectra and determined their nature and finally decomposed the spectra into their end-members. Because of the limited number of spectral bands, we collected only three spectral end-members (vegetation, soil and moisture) ideal to the accurate estimation of their sub-pixel fractions from the image data. The resulted fractions from LSMM were compared with normalised difference vegetation index (NDVI), ground truth data, as well as those estimates derived from the traditional hard classifier. NDVI values exhibited a positive correlation with vegetation fractions and negative correlation with soil fraction. Comparison with field data demonstrated higher reliability of the LSMM than the traditional approach of using predefined classification schemes with discrete numbers of cover types. The LSMM would seem to be well suited to locate the small wetland habitats that occurred as sub-pixel inclusions, and to represent continuous gradations between different habitat types in the study sites.

Continuous Gradations among Primary Carbonatitic, Kimberlitic, Melilititic, Basaltic, Picritic, and Komatiitic Melts in Equilibrium with Garnet Lherzolite at 3–8 GPa

Multianvil melting experiments in the system CaO–MgO–Al2O3– SiO2–CO2 (CMAS–CO2) at 3–8GPa, 1340–1800 � C, involving the garnet lherzolite phase assemblage in equilibrium with CO2-bearing melts, yield continuous gradations in melt composition between carbonatite, kimberlite, melilitite, komatiite, picrite, and basalt melts. The phase relations encompass a divariant surface in P–T space. Comparison of the carbonatitic melts produced at the low-temperature side of this surface with naturally occurring carbonatites indicates that natural magnesiocarbonatites could be generated over a wide range of pressures >2� 5GPa. Melts analogous to kimberlites form at higher temperatures along the divariant surface, which suggests that kimberlite genesis requires more elevated geotherms. However, the amount of water found in some kimberlites has the potential to lower temperatures for the generation of kimberlitic melts by up to 150 � C, provided no hydrous phases are present. Compositions resembling group IB and IA kimberlites are produced at pressures around 5–6GPa and 10GPa, respectively, whereas the compositions of some other kimberlites suggest generation at higher pressures still. At pressures <4GPa, an elevated geotherm produces melilitite-like meltinthe CMAS–CO2system ratherthan kimberlite. Even when a relatively CO2-rich mantle composition containing 0� 15 wt % CO2 is assumed, kimberlites and melilitites are produced by <1% melting and carbonatites are generated by even smaller degrees of melting of <0� 5%.